Abstract & Commentary
Synopsis: There were widespread beneficial effects of high amounts of exercise on plasma lipoproteins.
Source: Kraus WE, et al. N Engl J Med. 2002;347:1483-1492.
Increased physical activity is related to reduced risk of cardiovascular disease. This may be related to the improvement in plasma lipoproteins. However, the amount of exercise training required for optimal results is unknown. This randomized, prospective study investigated the effects of the amount and intensity of exercise on lipoproteins.
A total of 111 sedentary, overweight men and women with mild-to-moderate dyslipidemia were randomly assigned to participate for 6 months in a control group or for approximately 8 months in 1 of 3 exercise groups: high-amount-high-intensity exercise, the caloric equivalent of jogging 20 miles per week at 65-80% of peak oxygen consumption; low amount-high-intensity exercise, the equivalent of jogging 12 miles per week at 65-80% of peak oxygen consumption; or low amount moderate-intensity, the equivalent of walking 12 miles per week at 40-55% of peak oxygen consumption. Subjects were encouraged to maintain their base-line body weight. The 84 subjects who complied with these guidelines served as the basis for the main analysis. Detailed lipoprotein profiling was performed by nuclear magnetic resonance spectroscopy with verification by measurement of cholesterol in lipoprotein subfractions.
There was a beneficial effect of exercise on a variety of lipid and lipoprotein variables, seen most clearly with the high amount of high-intensity exercise. The high amount of exercise resulted in greater improvements than did the lower amount of exercise (in 10 of 11 lipoprotein variables) and was always superior to control conditions. Both lower amounts of exercise groups always had better responses than the control group.
The highest amount of weekly exercise, with minimal weight change, had widespread beneficial effects on the lipoprotein profile. The improvements were related to the amount of activity and not to the intensity of exercise or the improvements in fitness.
Comment by Ralph R. Hall, MD, FACP
So! More is better! Although the majority of exercise studies have demonstrated that the greater amount of exercise the more improvement in cardiovascular risk factors, newspapers and even the American College of Sports Medicine have downplayed the benefits of greater amounts of exercise. They have emphasized that even a little exercise is better than none, hoping to get the most sedentary of us to do a little. Many of us have been concerned that those doing moderate amounts of exercise would do less as result of the media’s emphasis on benefit of a small amount of exercise. The greatest benefit in the lipid profiles occurred in the high-amount high-intensity group. Tall in an accompanying editorial discusses the mechanisms that may influence these significant changes in the plasma lipids.1 He points out that the increase in plasma lipoprotein lipase increases the metabolism of VLDL and a decrease in hepatic lipase has a beneficial effect on HDL lipoproteins. This is a complicated process that we are just beginning to understand. It is illustrated by the recent work of Votruba and colleagues, which demonstrates exercise alters the way fat is metabolized and also that the change produced by exercise is dependent on the type of fat consumed.2
This study does not settle the argument about whether amount or intensity is more important in altering the plasma lipid levels. The low amount-high intensity group attained the same degree of fitness as the high amount-high intensity group. The low amount averaged the equivalent of 11 jogging miles per week while the large amount averaging 19 miles per week. One would expect the group exercising almost 2 times as much to attain the higher level of fitness. The fact that this did not happen implies that that there were nonresponders in the high amount-high intensity group or that there were actually errors in measuring the intensities between the groups. The authors corrected for the differences in fitness levels attained by men vs women by using peak oxygen consumption rather than the percent of maximum oxygen consumption. (Women attain lower levels of fitness, when fitness is measured by percent of maximum oxygen uptake—their percent of change is comparable to men when measured by peak oxygen uptake).3
Dr. Hall, Emeritus Professor of Medicine University of Missouri- Kansas City School of Medicine, is Associate Editor of Internal Medicine Alert.
1. Tall AT. N Engl J Med. 2002;347:1523-1524.
2. Votruba SB, et al. Med Sci Sports Exerc. 2002;34: 1757-1765.
3. Kanaley JA, et al. Eur J Appl Physiol. 2001;85:68-73.